diff --git a/version-2/find_broken_range_filters.rb b/version-2/find_broken_range_filters.rb
index b8a988f..989643d 100644
--- a/version-2/find_broken_range_filters.rb
+++ b/version-2/find_broken_range_filters.rb
@@ -6,7 +6,11 @@
 included_classes = ObjectSpace.each_object(Class).select do |klass|
   klass.included_modules.include?(Datagrid)
 end
-classes = [*included_classes, *Datagrid::Base.subclasses].uniq
+
+base_subclasses = ObjectSpace.each_object(Class).select do |klass|
+  klass < Datagrid::Base
+end
+classes = [*included_classes, *base_subclasses].uniq
 
 classes.flat_map(&:filters).select do |f|
   f.respond_to?(:range?) && f.range? && f.block